This invention relates to the separation of particles and more particularly to a method and apparatus for separating particles having different physical characteristics.
The present invention, while of general application, is particularly well suited for use in the separation of particles having different masses and magnetic characteristics. Industrial wastes such as finely divided siliceous slag, for example, commonly contain usable quantities of ferrous material and a substantial amount of vitreous particles which exhibit considerable variations in size. Particularly if the vitreous particles are separated to provide successive size gradations, they may be readily converted into glass spheres in the manner described, for example, in U.S. Pat. No. 2,945,326 granted July 19, 1960 to Thomas K. Wood, U.S. Pat. Nos. 3,560,186 and 3,560,185 granted Feb. 2, 1971 to Arthur G. Nylander, and U.S. patent application Ser. No. 450,089 filed Mar. 11, 1974 by Thomas A. Cerbo, now U.S. Pat. No. 3,877,918.
Heretofore, difficulties have been encountered in the separation of particles having different masses and magnetic characteristics. As an illustration, the magnetic particles often were entrapped in the siliceous slag or other waste material and could not be readily separated through conventional magnetic or electrostatic techniques. In addition, particularly for the finer size particles, the material often tended to agglomerate and when store for stored period of time under high humidity conditions formed comparatively cohesive lumps which interfered with the separation process. Furthermore, and this has been of special moment in centrifugal separation systems or systems in which the particles were fluidized, unwanted drafts or other air currents frequently resulted in incomplete separation.